Reaction of organosilane with glycerine-dicarboxylic acid ester and dicarboxylic acid



Patented Feb. 5, 1952 REACTION OF ORGAN OSILANE WITH GLYC-ERINEFDICARBOXYLIC ACID ESTER AND DICARBOXYLIC ACID John T. Goodwin,Jr.-', and Melvin J. Hunter, Midland, Micln, assignors to Dow CorningCorporation, Midland, Mich., a corporation of Michigan No Drawing.Application January I, 1950, Serial No. 137.471

1 Claim. (01. zoo-45.4)

1 This invention relates to resinous, thermosetting compositions ofmatter.

The copending application of Melvin J. Hunter et 8.1., Serial No.59,414, filed November 10, 1948,

discloses and claims resin compositions prepared by reacting a silanewith a polyhydric alcohol and thereafter reacting the product with apolybaslc acid. Resins prepared in this manner are of great utility ascoating compositions, such as paint vehicles and wire enamels. However,only a limited range of compositions can be prepared by this method, dueto incompatibility.

It is an object of this invention to prepare resinous materials whichpossess physical properties not obtainable by any previously knownmethod. Another object is to prepare resinous materials which combineheat stability; toughness, and solvent resistance to a degree heretoforeunknown.

In accordance with this invention a silane is reacted with a. glycerineester of a dicarboxylic acid. and the resulting silane-glyceride isreacted wiht an additional amount of an acidic compound of the groupdicarboxylic acids and anhydrides thereof.

The silanes of this invention have the formula RnSiX4-n where R is amonovalent hydrocarbon radical, X is alkoxy, acyloxy or chlorine, and nhas a value from 0.9 to 2.1.

The glycerine esters employed herein are the reaction product ofglycerine and a dicarboxylic acid or anhydride thereof, which materialsare reacted in amount such iyhat the ratio of glycerine OH to the acidgroups is from 2.25 :1 to 3 :1. Such esters have on the average from 3to 4 unreacted glycerine hydroxyls which are free to react with thesilane and additional acid. The reaction of the glycerine and acid iscarried out in the conventional manner for preparing glycerides.

The silane and the glycerine ester are reacted in amount so that theratio of silane X radicals to cess of carboxyl groups, or the silane Xradicals,

OH groups and carboxyl groups may be balanced. In this invention theterm acid group" has reference to carboxyl and anhydride groups, itbeing understood that an anhydride group is considered equivalent to twocarboxyl groups.

2 The basic reaction involved in preparing the silane-glycerine estermay be represented schematically as follows:

Reaction between the silane and the glycerine ester is produced bybringing the two into. contact, whereupon reaction begins at once withthe formation of the silane-glycerine ester and the elimination ofalcohol or hydrogen chloride. The reaction may be carried out attemperatures ranging from below 30 C. up to 250 C. In general, withchlorosilanes the reaction proceeds smoothly at room temperature,although in those cases in which the glycerine ester is quite viscous at30 C., it is desirable to heat the reaction mixture in order to insurethorough mixing of the reactants. When the silane X is alkoxy, it ispreferred that the reaction be carried out at temperatures between C.and 200 C. In either case the reaction is continued-until substantiallythe theoretical amount of by-product has been removed.

In the above-defined silanes any alkoxy group. such as for example,methoxy, ethoxy, butoxy, or stearyloxy, may be present.

Whereas resinous materials are obtained when any acyloxy group isemployed, for the purpose of this invention it is preferred that theacyloxy radical be one which contains at least seven carbon atoms.Examples of the preferred radicals which produce beneficialmodifications such asimproved solubility in hydrocarbon solvents arestearyloxy, 2-ethyl hexoyloxy, benzoyloxy, and linoleyloxy. Thus, it canbe seen that the hydrocarbon portion of the acyloxy group may be eithermonocyclic aryl, saturated aliphatic, or unsaturated aliphatic.

Acyloxy silanes may be prepared by reacting carboxyllc acids with alkoxysilanes or by reacting salts of carboxylic acids with chlorosilanes. Inthe former case an alcohol is the by-product, while in the latter thehalogen salt is split out.

The silanes employed in the method of this invention have from 0.9 to2.1 monovalent hydrocarbon radicals per silicon atom. It has been foundthat satisfactory coating compositions are obtained when saturatedaliphatic hydrocarbon radicals containing less than seven carbon atoms,such as methyl, ethyl, propyi, butyl, cyclohexyl, and cyclopentyl, andmonocyclic aryl radicals such as phenyl, tolyl, chlorophenyl and xylylare employed. It is to be understood that any combination of theabove-defined groups may be present in the silane and that the silanemay be. a p

3 mixture of SiXi, RSiXi, R2SiX2 and RaSiX so proportioned as to givethe above degree of substitution.

The glycerine esters employed herein are in the form of viscous fluidshaving a low degree of polymerization. Theoretically, the esters have anaverage degree of polymerization of and respond to the formulaHOCH2CHOHCH2OOCRCOOCH2CHOHCH2OH when the molar ratio of glycerine toacid is 2 and a mixture of the above and HOCI-IzCI-IOHCHzOOCRCOOH whenthe molar ratio is between 1.5 and 2. These esters are completelysoluble in polar organic solvents such as alcohols and are not resinousin character.

The acidic compounds employed to make the glycerine esters and to reactfurther with the silane-glycerine esters are dicarboxylic acids andanhydrides thereof. Any acid having the formula HOOCRCOOH or itsanhydride, in which R is a divalent aryl or divalent aliphatic radical,produces satisfactory resinous materials when employed in the method ofthis invention. Examples of such acids are phthalic, malonic, maleic andfumaric.

The silane-glycerine ester is reacted with an additional amount of theacidic compound. The reaction is carried out by heating a mixture of thetwo, preferably at a temperature between 100 C. and 250 C. Usually thetemperature is maintained between 175 C. and 210 C. Under theseconditions the acid reacts with the silaneglycerine ester to producepolymeric resinous materials. The reaction may proceed by either of twomechanisms. One is a condensation of an acid group with a glycerinehydroxyl, and the other is the splitting of the S100 linkages in theester, whereby the acid becomes attached directly to the silicon. Thisreaction may be represented schematically by the equation EsiOCE (RCO)'20- ESiOOCRCOOCE The latter phenomenon is readily observed when an acidanhydride is reacted with a silaneglycerine ester in which the ratio ofsilane X to OH is 1. In such an ester there are essentially no freeOI-Is. Yet the anhydride readily reacts with the ester, as is shown by arapid fall in the acid number and the resiniflcation of the product.

The reaction of the acid compound and the silane glycerine ester iscontinued until the desired state of polymerization is obtained. --Ithas been found convenient to stop the reaction when the product shows atendency to string or wrap around the agitator. In such a state theproduct is still soluble in solvents such as cyclohexanol, ketones, andaromatic hydocarbons. Thus, the material may be readily applied as asolution to the surfaces of a base member.

Normally, the above process is carried out in the absence of anysolvent. However, if desired, solvents such as aromatic hydrocarbons,alcohols, or ketones may be employed.

When the materials obtained by the above method are placed upon metalsurfaces and heated at temperatures of 100 to 250 C., a firmly adhering,hard, flexible, solvent-resistant coating is obtained. These coatingspossess a combination of thermal stability, stress-strain properties andresistance to solvents which are not shown by resins heretofore known.The thermal 4 stability approaches that of siloxane resins, while theirhigh flow-point and resistance to solvents at elevated temperature isessentially as good as thermosetting organic resins such as alkyds. Sucha combination of properties makes the resins prepared by the method ofthis invention eminently suitable for high-temperature magnet wireenamel and high-temperature paint vehicles.

The thermal stability of the instant materials is such that they may beheated at temperatures up to 250 C. for prolonged periods of timewithout appreciable decomposition.

The following examples are illustrative only of this invention.

Example 1 1.8 gram mols of phenylmethyldichlorosilane and .2 grammols-of phenyltrichlorosilane was added to the ester with agitation at atemperature of from 82 C. to 107 C. over a period of three hours. HClwas evolved, and heating was continued at 103 C. to 200 C. for anadditional six and a half hours. The reaction mixture was 'cooled to C.,and 1.9 gram mols of phthalic anhydride was added thereto. The mixturewas then heated at a temperature up to 206 C. for six hours, whereupon athermosetting resin was obtained.

Example 2 .6 gram mols of 2-ethyl hexoic acid was reacted with 0.5 grammols of phenyltriethoxysilane by heating the mixture for two hours at atemperature up to 197 C. 14 grams of ethyl alcohol distilled.

1.5 gram mols of glycerine was reacted with .75 gram mols of phthalicanhydride by heating a mixture of the two at a temperature of 200 C.until 15 grams of water distilled. The glyceryl phthalate was added tothe silane, and the mixture was heated at up to 180 C. for three hours,and 63 grams of ethyl alcohol was removed. .75 gram mols of phthalicanhydride was then added to the mixture, and heating was continued at180, C. The heating was continued until the mixture began to wrap aroundthe agitator, whereupon the mixture was diluted with 235 grams ofxylene. The resin was applied to the surface of a metal panel and baked,produced a satisfactory coating thereon.

Example 3 .5 gram mols of phthalic anhydride and 1 gram mol of glycerinewere heated at a temperature up to 180 C. and water was removed bydistillation. The resulting glyceryl phthalate was reacted with .5 grammols of phenylmethyldiethoxysilane at a temperature up to 210 C. Ethylalcohol distilled. After about the theoretical amount of alcohol hadbeen removed, .5 gram mols of phthalic anhydride was added to themixture, and heating at 180 C. was continued until the material showedsigns of gelation. The residue was dissolved in cyclohexanol.

A tin plate was coated with the resin solution and thereafter cured onehour at 200 C., wherethe copper wire, which broke at 30 per centelongation. The resin film had a softening point of 280 C. The scrapehardness was 13 after one hour in toluene at room temperature and aftersixteen hours at 80 C. at 90 per cent relative humidity. These proveexcellent solvent resistance and excellent resistance to moisture. The

above tests show that the resin is excellent for use as wire enamel.

Example 4 When 1 gram mol of phcnylmethyldiethoxwsilane is reacted with2 gram mols of 2-ethylhexoic acid at 170 C. to 200 C., 2 gram mols ofethyl alcohol is removed and the product is phenylmethyldi(2-ethylhexoyloxy) silane.

When this silane is reacted with the glyceryl phthalate of Example 1 inamount such that the ratio of acyloxy groups to OH is 0.5 and theresulting silane-glycerine ester is reacted with 'phthalic anhydride inamount such that the ratio of glycerine OH to the sum of acyloxy groupsplus total carboxyl' groups is 1, a thermosetting resin is obtained.

That which is claimed is:

The method of preparing resinous compositions which comprises reacting asilane of the formula RnS1X4-n, in which R is selected from the groupconsisting of saturated aliphatic radicals of less than seven carbonatoms and monocyclic aryl radicals, X is selected from the groupconsisting of alkoxy, acyloxy. and chlorine said formed by reactingglycerine with'an acidic compound selected from the group consisting ofdicarboxylic acids and anhydrides thereof in amount such that the ratioof glycerine OH to acid groups is from 2.25:1 to 3:1, said glycerineester being employed in amount such that the ratio of silane X radicalsto glycerine OH in excess of carboxyl radicals is from 0.1:1 to .5321and thereafter reacting the product thereby obtained with an acidiccompound selected from the group consisting of dicarboxylic acids andanhydrides thereof in amount such that the ratio of the sum of the totaldicarboxylic acid carboxyl radicals plus silane X radicals to glycerineOH radicals is from 1:0.9 to 1:1.2.

JOHN T. GOODWIN. JR. MELVIN J. HUNTER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,395,550 Iler et al. Feb. 26,1946 2,426,121 Rust et a1 Aug. 19, 1947 2,441,066 Hanford May 4, 19482,529,956 Myles et al. Nov. 14, 1950 FOREIGN PATENTS Number I CountryDate 583,754 Great Britain Dec. 30. 1946

